Heating pipe

ABSTRACT

A heating pipe includes a guide pipe, a connector and an outer pipe. A connector is disposed at one end of the guide pipe. The outer pipe surrounds the guide pipe and is positioned apart from the guide pipe. The heating pipe further includes two sealed elements positioned apart from each other and between the guide pipe and the outer pipe. The guide pipe, the outer pipe and the two sealed elements define a sealed room. A heating module is disposed in the sealed room.

RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201010111802.1, filed on Feb. 8, 2010 in the China Intellectual Property Office, the contents of which are hereby incorporated by reference. The application is also related to copending application entitled, “FLUID HEATER”, filed ______ (Atty. Docket No. US30480).

BACKGROUND

1. Technical Field

The present disclosure generally relates to a heating pipe.

2. Description of Related Art

In everyday life, industry or science research, a heated fluid is needed. Heating pipes are often used to guide and heat fluid, such as liquid or gas.

A conventional heating pipe includes an inner pipe and an outer pipe surrounding the inner pipe. The inner pipe and the outer pipe define a cavity. Heat wires are disposed in the inner pipe. In use of the conventional heating pipe, a fluid is guided in the cavity and heated by the heating wires in the inner pipe. However, because the fluid flowing in the cavity is disposed between the inner pipe and the outer pipe, the outer pipe conducts heat from the fluid to outside the heating pipe, and the heating efficiency of the heating pipe will be adversely affected. As such, the heating pipe has a low heating efficiency.

What is needed, therefore, is a heating pipe that can overcome the above-described shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is an isometric view of one embodiment of a heating pipe.

FIG. 2 is a cross-sectional view, along line II-II of FIG. 1.

FIG. 3 is an Scanning Electron Microscope (SEM) image of a drawn carbon nanotube film.

FIG. 4 is a schematic view of carbon nanotube segments in FIG. 3.

FIG. 5 is an SEM image of an untwisted carbon nanotube wire.

FIG. 6 is an SEM image of a twisted carbon nanotube wire.

FIG. 7 is an isometric view of the heating pipe of FIG. 1 with electrodes winding around an outer surface of a guide pipe.

FIG. 8 is a schematic view of a system for testing the heating pipe.

FIG. 9 is a relationship chart between a heating power of the heating pipe in FIG. 1 and a temperature of a liquid flowing in the heating pipe.

FIG. 10 is a cross-sectional view of another embodiment of a heating pipe.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.

Referring to FIGS. 1 and 2, a heating pipe 10 of one embodiment is shown. The heating pipe 10 includes a guide pipe 100, an outer pipe 102 surrounding the guide pipe 100, two sealed elements 110 disposed on an outer surface of the guide pipe 100, and a heating module 104 disposed between the guide pipe 100 and the outer pipe 102. The two sealed elements 110 contact two ends of the outer pipe 102, and are located between the guide pipe 100 and the outer pipe 102. The guide pipe 100, the two sealed elements 110, and the outer pipe 102 define a sealed room 120. The heating pipe 10 further includes a connector 1002 extending beyond the outer pipe 102 for connecting to another pipe and allowing a passage of fluid, such as a liquid or a gas.

The connector 1002 can extend beyond the outer pipe 102, and have the same inner diameter as the guide pipe 100. In another embodiment, the connector 1002 can be another pipe connected with the guide pipe 100, and have a different inner diameter than the inner diameter of the guide pipe 100. The connector 1002 can be an extended portion of the guide pipe 100 extending outside the outer pipe 102. The extended portion of the guide pipe 100 can be mechanically treated to form the connector 1002. For example, the connector 1002 can include a plurality of screw threads. Further, a fixed element 14 can be positioned on the connector 1002. The fixed element 14 can be used to fix the connector 1002 onto a conventional pipe. In this embodiment, the connector 1002 includes a plurality of screw threads, the fixed element 14 is a nut including a plurality of screw threads to mate with the screw threads of the connector 1002, until the connector 1002 is inserted and fixed into the fixed element 14. As such, the heating pipe 10 and the conventional pipe are connected by the connector 1002 and fixed by the fixed element 14.

The guide pipe 100 guides fluid flowing in the heating pipe 10. A cross sectional shape of the guide pipe 100 can be round, square, triangular, or elliptical. A material of the guide pipe 100 can be dielectric materials, such as glass, ceramic, polymer, resin, or quartz. The guide pipe 100 can also be made of conductive materials coated with dielectric materials. The length and the diameter of the guide pipe 100 are not limited, and can be determined according to the conventional pipe to which the heating pipe 10 will be connected. In one embodiment, the guide pipe 100 has a cylindrical shape with an outer diameter of about 5.12 millimeters, and a wall thickness of about 1.15 millimeters.

The heating module 104 can be located on an outer surface of the guide pipe 100 or on an inner surface of the outer pipe 102. In this embodiment, the heating module 104 is positioned on the outer surface of the guide pipe 100 and is separated from the inner surface of the outer pipe 102. The heating module 104 includes a heating element 1046, a first electrode 1042, and a second electrode 1044. The first electrode 1042 and the second electrode 1044 are electrically connected with the heating element 1046. The heating element 1046 is positioned on the outer surface of the guide pipe 100, with adhesive or by a mechanical method. The first electrode 1042 and the second electrode 1044 can be located on the same surface or different surfaces of the heating element 1046. In one embodiment according to FIG. 1, the first electrode 1042 and the second electrode 1044 are located on the same surface of the heating element 1046. The first electrode 1042 and the second electrode 1044 can be electrically connected with the circuit system with at least two lead wires (not shown).

The heating element 1046 can be metal wires, metal alloy wires, carbon fibers, or carbon nanotube structures. The carbon nanotube structure can be formed by screen printing method. The carbon nanotube structure can be a freestanding structure, namely, the carbon nanotube structure can support itself without a substrate. For example, if at least one point of the carbon nanotube structure is held, the entire carbon nanotube structure can be lifted without being destroyed. The carbon nanotube structure includes a plurality of carbon nanotubes joined by Van der Waals attractive force therebetween. The carbon nanotube structure can be a substantially pure structure of the carbon nanotubes, with few impurities. The carbon nanotubes can be used to form many different structures and provide a large specific surface area. The heat capacity per unit area of the carbon nanotube structure can be less than 2×10⁻⁴ J/m²*K. In one embodiment, the heat capacity per unit area of the carbon nanotube structure is less than or equal to 1.7×10⁻⁶ J/m²*K. Because the heat capacity of the carbon nanotube structure is very low, the temperature of the heating element 1046 can rise and fall quickly, and has a high response heating speed. Thus, the heating element 1046 has a high heating efficiency and accuracy. In addition, because the carbon nanotube structure can be substantially pure, the carbon nanotubes are not easily oxidized and the lifespan of the heating element 1046 will be relatively long. Furthermore, the carbon nanotube structure can have a small size, and the sealed room 120 can be small. As such, the heating pipe 10 will have an equally small size. Additionally, because the carbon nanotubes have a low density, about 1.35 g/cm³, the heating element 1046 is light. Because the carbon nanotube has a large specific surface area, the carbon nanotube structure with a plurality of carbon nanotubes has a larger specific surface area. If the specific surface of the carbon nanotube structure is large enough, the carbon nanotube structure is adhesive and can be directly applied to a surface.

The carbon nanotubes in the carbon nanotube structure can be orderly or disorderly arranged. The term ‘disorderly carbon nanotube structure’ refers to a structure where the carbon nanotubes are arranged along different directions, and the aligning directions of the carbon nanotubes are random. The number of the carbon nanotubes arranged along each different direction can be almost the same (e.g. uniformly disordered). The disorderly carbon nanotube structure can be isotropic, namely the carbon nanotube structure has properties identical in all directions of the carbon nanotube structure. The carbon nanotubes in the disorderly carbon nanotube structure can be entangled with each other.

The term ‘ordered carbon nanotube structure’ refers to a structure where the carbon nanotubes are arranged in a consistently systematic manner, e.g., the carbon nanotubes are arranged approximately along a same direction and/or have two or more sections within each of which the carbon nanotubes are arranged approximately along a same direction (different sections can have different directions). The carbon nanotubes in the carbon nanotube structure can be selected from single-walled, double-walled, and/or multi-walled carbon nanotubes.

The carbon nanotube structure can be a layered carbon nanotube structure, a linear carbon nanotube structure or combinations thereof. If the carbon nanotube structure is a layered structure, the carbon nanotube structure can wrap the outer surface of the guide pipe 100. If the carbon nanotube structure includes a single linear carbon nanotube structure, the single linear carbon nanotube structure can spirally twist about the guide pipe 100. If the heating element 1046 includes two or more linear carbon nanotube structures, the linear carbon nanotube structures can be disposed on the outer surface of the guide pipe 100 and be substantially parallel with each other. The linear carbon nanotube structures can be disposed side by side or separately. If the carbon nanotube structure includes a plurality of linear carbon nanotube structures, the linear carbon nanotube structures can be knitted to obtain a net structure disposed on the outer surface of the guide pipe 100.

The carbon nanotube structure with layer structure includes at least one carbon nanotube film. In one embodiment, the carbon nanotube film is a drawn carbon nanotube film. A film can be drawn from a carbon nanotube array, to obtain a drawn carbon nanotube film. The drawn carbon nanotube film includes a plurality of successive and oriented carbon nanotubes joined end-to-end by Van der Waals attractive force therebetween. The drawn carbon nanotube film is a free-standing film. Each drawn carbon nanotube film includes a plurality of successively oriented carbon nanotube segments joined end-to-end by Van der Waals attractive force therebetween. Each carbon nanotube segment includes a plurality of carbon nanotubes substantially parallel to each other, and joined by Van der Waals attractive force therebetween. Some variations can occur in the drawn carbon nanotube film. The carbon nanotubes in the drawn carbon nanotube film are oriented along a preferred orientation. The carbon nanotube film can be treated with an organic solvent to increase the mechanical strength and toughness of the carbon nanotube film and reduce the coefficient of friction of the carbon nanotube film. The thickness of the carbon nanotube film can range from about 0.5 nm to about 100 μm.

The carbon nanotube structure of the heating element 1046 can include at least two stacked carbon nanotube films. In other embodiments, the carbon nanotube structure can include two or more coplanar carbon nanotube films, and can include layers of coplanar carbon nanotube films. Additionally, if the carbon nanotubes in the carbon nanotube film are aligned along one preferred orientation (e.g., the drawn carbon nanotube film) an angle can exist between the orientations of carbon nanotubes in adjacent films, whether stacked or adjacent. Adjacent carbon nanotube films can be joined by only the Van der Waals attractive force therebetween. The number of the layers of the carbon nanotube films is not limited. However, the thicker the carbon nanotube structure is, the smaller the specific surface area. An angle between the aligned directions of the carbon nanotubes in two adjacent carbon nanotube films can range from about 0 degrees to about 90 degrees. The carbon nanotubes in the heating element 1046 define a microporous structure. The carbon nanotube structure in an embodiment employing these films will have a plurality of micropores. Stacking the carbon nanotube films will also add to the structural integrity of the carbon nanotube structure.

In other embodiments, the carbon nanotube film can be a flocculated carbon nanotube film. The flocculated carbon nanotube film can include a plurality of long, curved, disordered carbon nanotubes entangled with each other. Furthermore, the flocculated carbon nanotube film can be isotropic. The carbon nanotubes can be substantially uniformly dispersed in the carbon nanotube film. Adjacent carbon nanotubes are acted upon by Van der Waals attractive force to obtain an entangled structure with micropores defined therein. It is noteworthy that the flocculated carbon nanotube film is very porous. Sizes of the micropores can be less than 10 μm. The porous nature of the flocculated carbon nanotube film will increase the specific surface area of the carbon nanotube structure. Further, due to the carbon nanotubes in the carbon nanotube structure being entangled with each other, the carbon nanotube structure employing the flocculated carbon nanotube film has excellent durability, and can be fashioned into desired shapes with a low risk to the integrity of the carbon nanotube structure. The thickness of the flocculated carbon nanotube film can range from about 0.5 nm to about 1 mm.

In other embodiments, the carbon nanotube film can be a pressed carbon nanotube film. The pressed carbon nanotube film can be a free-standing carbon nanotube film. The carbon nanotubes in the pressed carbon nanotube film are arranged along a same direction or along different directions. The carbon nanotubes in the pressed carbon nanotube film can rest upon each other. Adjacent carbon nanotubes are attracted to each other and are joined by Van der Waals attractive force. An angle between a primary alignment direction of the carbon nanotubes and a surface of the pressed carbon nanotube film is about 0 degrees to approximately about 15 degrees. The greater the pressure applied, the smaller the angle obtained. If the carbon nanotubes in the pressed carbon nanotube film are arranged along different directions, the carbon nanotube structure can be isotropic. Here, “isotropic” means the carbon nanotube film has properties identical in all directions substantially parallel to a surface of the carbon nanotube film. The thickness of the pressed carbon nanotube film ranges from about 0.5 nm to about 1 mm.

The linear carbon nanotube structure includes at least one carbon nanotube wire. The carbon nanotube wire can be untwisted or twisted. Treating the drawn carbon nanotube film with a volatile organic solvent can obtain the untwisted carbon nanotube wire. In one embodiment, the organic solvent is applied to soak the entire surface of the drawn carbon nanotube film. During the soaking process, adjacent parallel carbon nanotubes in the drawn carbon nanotube film will bundle together, due to the surface tension of the organic solvent as it volatilizes, and thus, the drawn carbon nanotube film will be shrunk into an untwisted carbon nanotube wire. Referring to FIG. 5, the untwisted carbon nanotube wire includes a plurality of carbon nanotubes substantially oriented along a same direction (i.e., a direction along the length direction of the untwisted carbon nanotube wire). The carbon nanotubes are substantially parallel to the axis of the untwisted carbon nanotube wire. In one embodiment, the untwisted carbon nanotube wire includes a plurality of successive carbon nanotube segments joined end to end by Van der Waals attractive force therebetween. Each carbon nanotube segment includes a plurality of carbon nanotubes substantially parallel to each other, and combined by Van der Waals attractive force therebetween. The carbon nanotube segments can vary in width, thickness, uniformity, and shape. The length of the untwisted carbon nanotube wire can be arbitrarily set as desired. A diameter of the untwisted carbon nanotube wire ranges from about 0.5 nm to about 100 μm.

The twisted carbon nanotube wire can be obtained by twisting a drawn carbon nanotube film using a mechanical force to turn the two ends of the drawn carbon nanotube film in opposite directions. Referring to FIG. 6, the twisted carbon nanotube wire includes a plurality of carbon nanotubes helically oriented around an axial direction of the twisted carbon nanotube wire. In one embodiment, the twisted carbon nanotube wire includes a plurality of successive carbon nanotube segments joined end to end by Van der Waals attractive force therebetween. Each carbon nanotube segment includes a plurality of carbon nanotubes substantially parallel to each other, and combined by Van der Waals attractive force therebetween. The length of the carbon nanotube wire can be set as desired. A diameter of the twisted carbon nanotube wire can be from about 0.5 nm to about 100 μm. Further, the twisted carbon nanotube wire can be treated with a volatile organic solvent after being twisted. After being soaked by the organic solvent, the adjacent substantially parallel carbon nanotubes in the twisted carbon nanotube wire will bundle together, due to the surface tension of the organic solvent when the organic solvent volatilizes. The specific surface area of the twisted carbon nanotube wire will decrease, while the density and strength of the twisted carbon nanotube wire will increase.

The heating element 1046 can be a carbon nanotube composite structure. The carbon nanotube composite structure includes the carbon nanotube structure disclosed above and matrix materials. The matrix materials are filled in the carbon nanotube structure or are disposed on at least one surface of the carbon nanotube structure. In other embodiments, the matrix material can surround the carbon nanotube structure. The matrix materials can be metal, resin, ceramic, glass, or fiber.

The first electrode 1042 and the second electrode 1044 can be fixed on the surface of the heating element 1046 by conductive adhesive (not shown). The first electrode 1042 and the second electrode 1044 are made of conductive material. The shapes of the first electrode 1042 and the second electrode 1044 are not limited and can be lamellar, rod, or wire shaped. The cross sectional shape of the first electrode 1042 and the second electrode 1044 can be round, square, trapezium, triangular, or polygonal. The thickness of the first electrode 1042 and the second electrode 1044 can be any size, depending on the design, and can be about 1 micrometer to about 1 centimeter. In the present embodiment as shown in FIG. 1, the first electrode 1042 and the second electrode 1044 both have a linear shape, and are positioned on the surface of the heating element 1046, and substantially parallel with an axial direction of the guiding pipe 100. The first electrode 1042 and the second electrode 1044 are substantially parallel with each other. In one embodiment, if the heating element 1046 includes the carbon nanotube structure having a plurality of carbon nanotubes arranged in substantially the same direction, the carbon nanotubes are oriented from the first electrode 1042 to the second electrode 1044.

In another embodiment according to FIG. 7, the first electrode 1042 and the second electrode 1044 are separately positioned on two opposite ends of the guide pipe 100. The first electrode 1042 and the second electrode 1044 wind around the guide pipe 100 to form two ring structures. If the heating element 1046 includes the carbon nanotube structure having a plurality of carbon nanotubes arranged in a same direction, the carbon nanotubes are oriented from the first electrode 1042 to the second electrode 1044.

In other embodiments, the heating module 104 can include a plurality of first electrodes 1042 and a plurality of second electrodes 1044. The number of the first electrodes 1042 and the number of the second electrodes 1044 can be the same. The first electrodes 1042 and the second electrodes 1044 are alternatively positioned on a surface of the heating element 1046. The carbon nanotube structure disposed between every adjacent first electrode 1042 and second electrode 1044 can be electrically connected in parallel with each other.

In one embodiment, the heating element 1046 includes a single linear carbon nanotube structure spirally twisted about the guide pipe 100, with the first electrode 1042 and the second electrode 1044 can be omitted.

The outer pipe 102 covers the heating module 104. The outer pipe 102 is configured for keeping the heating module 104 away from contamination from the environmental surroundings, and can protect the user from getting an electric shock when touching the heating pipe 10. An inner diameter of the outer pipe 102 is larger than an outer diameter of the guide pipe 100. In this embodiment, the outer pipe 102 and the guide pipe 100 are coaxial. The sealed room 120 defined by the outer pipe 102, the guide pipe 100, and the two sealed elements 110 can be in a vacuum-like state. The sealed room 120 can be used to reduce the less of the heat produced by the heating element 1046. The material of the outer pipe 102 can be conductive or insulated. The electrically conductive material can be metal or alloy. The metal can be copper, aluminum, or titanium. The insulated material can be resin, ceramic, plastic, or wood. The resin can be acrylic, polypropylene, polycarbonate, polyethylene, epoxy resin, or PTFE. The material of the outer pipe 102 can be flexible. If the materials of the guide pipe 100 and the outer pipe 102 are both flexible, the heating pipe 10 can be flexible according to determination. The thickness of the outer pipe 102 can range from about 0.5 μm to about 2 mm. If the material of the outer pipe 102 is insulative, the outer pipe 102 can be directly disposed on a surface of the heating module 104. If the outer pipe 102 is conductive, the outer pipe 102 should be insulated from the heating module 104.

The heating pipe 10 can further include a heat-reflective layer 112 positioned on the inner surface of the outer pipe 102. The heat-reflective layer 112 is apart from the heating module 104. The heat-reflective layer 112 is configured to reflect back the heat emitted by the heating module 104, and control the direction of the heat emitted by the heating module 104. The material of the heat-reflective layer 112 can be selected from conductive material or insulative material. The insulative material can be metal oxides, metal salts, or ceramics. The conductive material can be silver, aluminum, gold or alloy. A thickness of the heat-reflective layer 112 can be in a range from about 100 micrometers to about 0.5 millimeters.

The heating pipe 10 can alternatively include a heat-insulated layer 130 positioned on an outer surface of the outer pipe 102. A material of the heat-insulated layer 130 can be asbestos, diatomite, perlite, glass fiber, or combination thereof. The heat-insulated layer 130 reduces the loss of the heat produced by the heating module 104.

In use, if a voltage is applied to the first electrode 1042 and the second electrode 1044 of the heating pipe 10 by a power wire 106, the carbon nanotube structure can radiate heat at a certain wavelength. The heating pipe 10 can further include a temperature-controlling element 108 to detect and control the temperature of the heating pipe 10. The temperature of the heating pipe 10 detected by the temperature-controlling element 108 can be changed by changing some parameters of the heating pipe 10 and the fluid guided into the heating pipe 10, such as a voltage between the first electrode 1042 and the second electrode 1044 and/or a flow rate of the fluid. In one embodiment, the temperature-controlling element 108 is electrically connected in series with the heating pipe 10.

The heating pipe 10 can be used as a fluid pipe directly or be connected with one end of a fluid pipe. The heating pipe 10 can heat the fluid flowing through the guiding pipe 100 of the heating pipe 10. If the voltage between the first electrode 1042 and the second electrode 1044 is kept unchanged, a temperature of the liquid will be uniform when it reaches a steady state. The temperature-controlling element 108 can also be used to control the temperature of the fluid.

In one embodiment, the heating effect of the heating pipe 10 is tested in test equipment as shown in FIG. 8. The test equipment includes a first container 60, a pump 30, the heating pipe 10, and a second container 40. The guide pipe 100 has a larger length than the heating pipe 10 and connects the first container 60 and the second container 40. The guide pipe 100 is able to move liquid 50 from the first container 60 to the second container 40 by the pump 30. The liquid 50 is heated by the heating pipe 10 when it flows from the guide pipe 100 of the heating pipe 10. In one embodiment, the liquid 50 is water, and the guide pipe 100 is a cylindrical rubber pipe having an outer diameter of about 5.12 millimeters and a thickness of the wall of about 1.15 millimeters. The outer pipe 102 is made of polytetrafluoroethylene (PTFE), an inner diameter of the outer pipe 102 is about 6.36 millimeters, and a thickness of the wall of the outer pipe 102 is about 1.35 millimeters. The sealed elements 110 are made of plastic. The first electrode 1042 and the second electrode 1044 are copper wires. The first electrode 1042 and the second electrode 1044 are oriented along the axis direction of the guide pipe 100. The heating element 1046 is the drawn carbon nanotube film with a width of about 5 centimeters. The drawn carbon nanotube film wraps an outer surface of the guide pipe 100. The first electrode 1042 and the second electrode 1044 are positioned on an outer surface of the heating element 1046. The carbon nanotubes in the drawn carbon nanotube film are oriented from the first electrode 1042 to the second electrode 1044.

In the embodiment according to FIG. 8, a flow rate of the liquid 50 is about 3.53 ml/min. A temperature of the liquid 50 in the first container 60, which is not heated by the heating pipe 10 is about 24 centigrades. The liquid 50 in the second container 40, which is heated by the heating pipe 10 when it passes the heating pipe 10, has a temperature determined by a heating power of the heating pipe 10. A voltage between the first electrode 1042 and the second electrode 1044 and the current of the heating element 1046 determines the heating power. The relationship of the voltage, the current, the heating power and the temperature of the liquid 50 in the second container 40 is tested. The test result is shown in Table 1.

TABLE 1 Testing result of the heating pipe 10 Voltage Current heating temperature of (V) (A) power (W) the liquid (° C.) 3.1 0.3 0.93 30 4.5 0.4 1.80 34 6.0 0.6 3.60 41 7.5 0.9 6.75 53 9.0 1.2 10.8 72

It can be seen from Table 1 that the liquid 50 passing through the heating pipe 10 can be sufficiently heated at a low voltage. In the test process, the liquid 50 can reach a predetermined temperature in 30 minutes, and the heating effect is stable and uniform.

Referring to FIG. 9, a temperature difference between the liquid 50 in the first container 60 and the liquid 50 in the second container 40 has a linear relationship with the heating power. The heating pipe 10 can uniformly heat the flowing liquid 50.

Referring to FIG. 10, a heating pipe 20 according to another embodiment is provided. The heating pipe 20 includes a guide pipe 200, an outer pipe 202 surrounding the periphery of the guide pipe 200, two sealed elements 210 positioned on an outer surface of the guide pipe 200 and a heating module 204 positioned between the guide pipe 200 and the outer pipe 202. The two sealed elements 210 contact with two ends of the outer pipe 202, and are located between the guide pipe 200 and the outer pipe 202. A sealed room 220 is defined by the guide pipe 200, the two sealed elements 210, and the outer pipe 202. The heating module 204 includes a heating element 2046, a first electrode 2042 and a second electrode 2044. The heating element 2046 is attached to an inner surface of the outer pipe 202, and is spaced from the guide pipe 200. In some embodiments, the heating element 2046 can also be clamped between the outer pipe 202 and the guide pipe 200, and the first electrode 2042 and the second electrode 2044 can each be a layer of conductive material coated on the heating element 2046.

The heating pipe 20 further includes a heat-reflective layer 212 disposed on an outer surface of the heating element 2046. The material of the heat-reflective layer 212 is an insulative material.

Other characteristics of the heating pipe 20 are the same as the heating pipe 10 disclosed above.

The heating pipe disclosed in the present disclosure can be used to heat the fluid flowing through the heating pipe. The heating pipe can be used in many fields, such as pre-heating air in a boiler of power station to improve production efficiency, heating a pipe in different sections in a laboratory to control catalytic effect of enzyme, heating liquid medicine before it is injected into a patient to make the patient comfortable or improve the medical effect, and heating running water for everyday life or for industry.

It is to be understood that the above-described embodiments are intended to illustrate rather than limit the present disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. It is understood that any element of any one embodiment is considered to be disclosed to be incorporated with any other embodiment. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure. 

1. A heating pipe comprising: a guiding pipe; an outer pipe surrounding the guiding pipe and apart from the guiding pipe; a connector disposed at one end of the guiding pipe and extending beyond the outer pipe; two sealed elements apart from each other and sealed between an outer surface of the guiding pipe and an inner surface of the outer pipe, wherein the guiding pipe, the outer pipe, and the two sealed elements cooperatively define a sealed room; and a heating module positioned in the sealed room.
 2. The heating pipe of claim 1, wherein the connector is an end portion of the guiding pipe 100 extending beyond the outer pipe, and an inner diameter of the connector is substantially the same as an inner diameter of the guiding pipe.
 3. The heating pipe of claim 1, wherein the connector is a separate pipe connected with the guiding pipe.
 4. The heating pipe of claim 1, wherein the sealed room is in a vacuum-like state.
 5. The heating pipe of claim 1, further comprising a heat-reflective layer located between the heating module and the outer pipe.
 6. The heating pipe of claim 5, wherein the heat-reflective layer is located on the inner surface of the outer pipe.
 7. The heating pipe of claim 6, wherein the heating module is positioned on the outer surface of the guiding pipe and apart from the heat-reflective layer.
 8. The heating pipe of claim 5, wherein the heat-reflective layer is made of insulative material and positioned on a surface of the heating module.
 9. The heating pipe of claim 1, wherein the heating module comprises a heating element, a first electrode, and a second electrode, the first electrode and the second electrode being electrically connected with the heating element.
 10. The heating pipe of claim 9, wherein the heating element comprises a freestanding carbon nanotube structure comprising a plurality of carbon nanotubes joined by Van der Waals attractive force.
 11. The heating pipe of claim 10, wherein the carbon nanotube structure comprises at least one carbon nanotube film wrapping the outer surface of the guiding pipe.
 12. The heating pipe of claim 11, wherein the at least one carbon nanotube film comprises a plurality of carbon nanotubes joined end-to-end with each other and oriented in a substantially same direction.
 13. The heating pipe of claim 12, wherein the first electrode and the second electrode each have a wire structure and are substantially parallel with an axial direction of the guiding pipe, and the carbon nanotubes in the carbon nanotube film are oriented from the first electrode to the second electrode.
 14. The heating pipe of claim 12, wherein the first electrode and the second electrode each have a ring structure and are wound around two opposite ends of the guiding pipe; the carbon nanotubes in the carbon nanotube film are oriented from the first electrode to the second electrode.
 15. The heating pipe of claim 9, wherein the carbon nanotube structure comprises at least one linear carbon nanotube structure disposed on the outer surface of the guiding pipe.
 16. A heating pipe comprising: a guiding pipe; an outer pipe surrounding the guiding pipe and apart from the guiding pipe; a connector disposed at one end of the guiding pipe and extending beyond the outer pipe for connecting another pipe and allowing a passage of fluid; two sealed elements apart from each other and located between the guiding pipe and the outer pipe, wherein a sealed room is cooperatively defined by the guiding pipe, the outer pipe and the two sealed elements; and a heating module disposed in the sealed room, the heating module comprising a heating element comprising a carbon nanotube structure positioned on an outer surface of the guiding pipe.
 17. The heating pipe of claim 16, wherein a heat capacity per unit area of the carbon nanotube structure is less than 2×10⁻⁴ J/m²*K.
 18. The heating pipe of claim 16, wherein the carbon nanotube structure comprises one linear carbon nanotube structure twisted around the outer surface of the guiding pipe.
 19. The heating pipe of claim 16, wherein the carbon nanotube structure comprises a plurality of linear carbon nanotube structures disposed side by side and substantially parallel with each other on an outer surface of guiding pipe.
 20. The heating pipe of claim 16, wherein the carbon nanotube structure comprises a plurality of linear carbon nanotube structures knitted to obtain a net structure disposed on an outer surface of the guiding pipe. 